It has been known to take discarded used mattresses which are still in reasonable condition and refurbish same for resale as used mattresses by subjecting same to a sanitizing process which is covered by laws in certain jurisdictions such as California and Pennsylvania.
This sanitizing process includes heating the used mattress to some 110 to 116 degrees Celsius (230 to 240 degrees Fahrenheit) as well as treating same with chemical disinfectants. Such refurbished mattresses can then be sold as used products.
It is also known to refurbish a used mattress by removing the outer ticking and padding material from the inner spring assembly, straightening bent components on the inner spring assembly and then attaching new ticking and padding material to the inner spring assembly. However, the inner spring assembly will have suffered some fatigue from use and, although the refurbishing activity may provide some local improvements within the assembly, on balance the inner spring assembly will have a reduced load bearing capacity than when new. Such refurbished mattresses are therefore inferior to the original mattress when it was new. While they may be returned to their owners, such refurbished matresses cannot be sold to the general public except as product containing used material.
The basic component of most spring filled mattresses is of course the inner spring assembly whose construction has remained essentially unchanged for nearly a century. This inner spring assembly comprises a series of hour glass shaped coils of heavy wire arranged in rows and tied together in their rows by various means such as pigtails or crimp rods formed of much lighter wire than the coils. Border wires tied to the boundary coils surround the inner spring assembly. The inner spring assembly of many box springs is generally similar to that of a mattress except that the coils have an inverted cone shape and, since the assembly is attached at the bottom to a wooden frame, the border wire and connecting wire are only fastened to the top side of the coils.
The components of the inner spring assembly are all made of metal wire which becomes stressed at positions where significant permanent bending of the wire takes place and results in a reduction of the load bearing capacity of the wire at said positions. In a new inner spring assembly, this stressing happens when the wire is formed into a shape such as the hour glass coil or the border wire or when the the wire is bent or wrapped to join the other components as in the case of crimp rods and pigtails. These stresses can be relieved to a greater or lesser extent, depending on the temperature and duration of the heating process, by heating the wire and then allowing the wire to cool in air to room temperature which results in an improvement in the wire's mechanical properties and a corresponding improvement in the load bearing capacity of the inner spring assembly.
By contrast, a minor bending of the border wire, pigtail wire or crimp rods will actually increase the load bearing capacity of these wires at the location of the bend. Accordingly, the minor bending of said wires, which occurs when the mattress is subjected to heavy use, followed by an opposite bending of the same wires to restore their position actually improves the local mechanical properties of said wire.
The individual hour glass shaped coils are normally subjected to a brief and often uneven heat treatment process that partially relieves stresses after their formation. Sometimes the border wires and wire elements tying the spring coils together are not stress relieved. In some instances they are briefly heated to obtain a partial relief of stresses. Because these components are either not stress relieved or only partially stress relieved, the inner spring assembly can be improved by subsequent heat treatments.
In use the inner spring covering of ticking and padding material and the like is subjected to staining, ripping, lumping and tearing. Under normal use, the border wires and connecting wire elements sometimes experience minor bending. Under heavy use, the coil springs may in fact shift out of proper position or, in rare instances, become distorted or broken. However, in most cases, even after long time usage, the load bearing capacity of the individual coils is substantially unimpaired so that a subsequent heat treatment of the inner spring assembly actually improves the load bearing capacity of the individual coils compared to when new.
Moreover because the inner spring assembly is enclosed by the ticking and padding material, it is essentially protected from oxidation which could deleteriously affect the wire members including the hour glass coils.
Recognizing that in most cases the coils of an inner spring assembly remain substantially unimpaired in use even in mattresses that had long time usage coupled with a realization that the quality of metal which has been subject to a partial heat treating stress relieving process can be further improved by subsequent or additional heat treating processes led to the present invention of being able to use the inner spring assembly of used mattresses or similar inner spring containing products to produce new mattresses or similar inner spring containing products having qualities superior to the original products when they were new warranting sale of the products of the present invention as new products.